Central Asia’s Aral Sea, which used to be the world’s fourth-largest lake, has shrunk so dramatically that it has split into two separate bodies of water. The two rivers that feed it were diverted in the 1960s to water cotton fields; now just a trickle reaches the sea, and much of that is contaminated by pesticides and fertilizers. As the sea has receded, villages and small cities that used to be bustling metropolises have become dusty ghost towns. One such town, the former port of Aralsk, Kazakhstan, now lies about 55 miles from the Aral Sea. Fishing and shipping industries in the town have disappeared, textiles and electronics factories have closed up shop, and agriculture is suffering from desertification and heavily salinized water. The sea’s retreat has brought colder winters and hotter summers, and the incidences of anemia, tuberculosis, infant mortality, cancer, and respiratory disease are all on the rise.